Integumentary System 3: Wounds

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Epidermal and Dermal Wound Healing

Epidermal Wounding Healing:
  1. Basal cells of epidermis break contact with the basement membrane
  2. Cells enlarge and migrate across the wound, which is stimulated by epidermal growth factor (EGF)
  3. Migration of cells stops due to contact inhibition
  4. Relocated cells divide to build new epidermal layers and thicken epidermis
Deep Wound Healing (into dermis and/or subcutaneous layer):
  1. Inflammatory phase: blood clot forms loosely binding wound edges, causing inflammation
  2. Migratory phase: clot becomes a scab, epithelial cells migrate beneath the scab to bridge the wound, fibroblasts migrate and form collagen
  3. Proliferative phase: extensive growth of epithelial cells beneath the scab, collagen fibres randomly deposited, blood vessels grow
  4. Maturation phase: collagen fibres become organised, epithelium is restored to normal thickness, scab sloughs off

Photo damage

There are three types of photo light, some which are blocked and some which cause damage:
  • UVA causes long term damage from skin tanning
  • UVB is the main cause of sunburn due to DNA damage in epithelial cells
  • UVC is normally stopped by the ozone layer

Burns

Burns to more than 20% of the body can be life-threatening. Any partial of full thickness burn that involves the genitals, eyes, ears, hands, feet or burns over major joints need medical car. There are three types of burns:
  • First degree: superficial discomfort due to damaged epidermal layer → couple of days healing
  • Second degree: dermal layer damaged → weeks of healing
  • Third degree: full thickness of skin is damaged → months to years of damage with complications, e..g infections

Effects of ageing on the skin

Like other parts of the body, the skin loses strength and motility as we age. The following points are seen through age:
  • Increased skin injuries and infections
  • Immune system is reduced
  • Muscles become weaker
  • Decrease in bone strength
  • Increase sensitivity to the sun
  • Skin dries and becomes scaly
  • Hair changes
  • Reduced ability to lose heat
  • Ability of skin to repair is lost








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